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/*Copyright (c) 2011, Florent DEVILLE.                                      */
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#include "RTSpotLight.h"
#include "RTMatrix44.h"

#include <math.h>

namespace RT
{
	/*Default constructor*/
	RTSpotLight::RTSpotLight(): m_location(0, 0, 0), m_direction(1, 0, 0), m_cutOffAngle(1.57f), m_beamAngle(0.6f),
		m_attenuation(0, 0, 0)
	{
		m_lightColor = RTColor(1, 1, 1, 1);
		m_type = eSpotLight;
	}

	/*Constructor*/
	RTSpotLight::RTSpotLight(const RTColor& color, const RTVector3f& location, const RTVector3f& direction, F32 cutOff,
						   F32 beam, const RTVector3f& attenuation):m_location(location), m_direction(direction),
						   m_cutOffAngle(cutOff), m_beamAngle(beam), m_attenuation(attenuation)
	{
		m_lightColor = color;
		m_direction.normalize();
		m_type = eSpotLight;
	}

	/*Destructor*/
	RTSpotLight::~RTSpotLight(){}

	/*Compute light color*/
	RTColor RTSpotLight::computeColor(const RTRay& ray, F32 dist)const
	{
		//calculate attenuation
		F32 A = 1;
		if(m_attenuation.norme2() != 0)
			A = m_attenuation.x + m_attenuation.y * dist + m_attenuation.z * dist * dist;

		//calculate itensity
		F32 theta = acos((-ray.getDirection()).dot(m_direction));
		theta = fabs(theta);

		F32 I = 1;
		if(theta > m_cutOffAngle)
			I = 0;
		else if (theta > m_beamAngle)
		{
			//I = (m_cutOffAngle - m_beamAngle) / m_cutOffAngle -(theta - m_beamAngle);
			I = (theta - m_cutOffAngle) / (m_beamAngle - m_cutOffAngle);
		}


		//return color
		return m_lightColor * I / A;
	}

	/*Compute the light's shadow ray*/
	void RTSpotLight::computeShadowRay(const RTVector3f& point, RTRay& shadowRay, F32* distance)const
	{
		//get a ray from the object to the light
		RTVector3f L = m_location - point; //vector from the point of the object to the light
		*distance = L.norme();
		L.normalize();

		//to avoid intersection with itslef
		shadowRay.setOrigin(point + (L * 0.01f));
		shadowRay.setDirection(L);
	}

	/*Apply the view matrix to the light*/
	void RTSpotLight::applyViewMatrix(const RTMatrix44& view)
	{
	
		m_location = m_location * view;

		RTVector3f dirS = RTVector3f(0, 0, 0) * view;
		RTVector3f dirE = m_direction * view;
		m_direction = dirE - dirS;
		m_direction.normalize();
	}

}